Fiber optic gyroscopes are used in a variety of applications to detect changes in orientation. For example, fiber optic gyroscopes can be used in the navigation systems of guided missiles and vehicles such as aircraft, spacecraft, ships, and submarines.
Fiber optic gyroscopes operate based on the interference generated by beams of light. In a conventional fiber optic gyroscope, a fiber optic cable is coiled, and beams of light are injected into the coil at opposite ends of the coil. Due to the Sagnac effect, rotation of the coil causes the light beam traveling in the direction of rotation to experience a slightly longer path delay than the light beam traveling in the opposite direction. This creates a small phase shift between the beams of light. This phase shift can be measured and used to precisely identify the angular velocity of the rotation experienced by the coil.